The present invention relates to parts used in electric motors and, more particularly, to apparatus for making stator assemblies comprising a laminated magnetic core and windings that are primarily adapted for being bolted to mounting means within a hermetically sealed refrigeration compressor.
Substantial work has been done heretofore in order to prevent loss of bolt torque retention and to maintain a concentric air gap. For example, Hull U.S. Pat. No. 3,299,304 and Sisk U.S. Pat. No. 3,465,188 are both directed at solving this problem. While these patents primarily describe what are known as "bonded cores", unbonded cores are also described in the art by, e.g., British Pat. No. 1,192,791 which was published May 20, 1970. Moreover, specific methods aimed at maintaining straight and concentric bores are described in Reynolds U.S. Pat. No. 3,845,547, and Gerstle U.S. Pat. No. 3,834,013. In the interest of brevity, the entire disclosures of all of the patents just mentioned are now expressly incorporated herein by reference for background purposes.
Another patent which describes equipment and methods pertaining to axially compressed but unbonded cores is McMahon U.S. Pat. No. 3,605,257. Generally, the approaches suggested by the above-mentioned patents are less than fully satisfactory when unbonded cores are to be produced, and problems still remain in producing unbonded hermetic cores that will exhibit both good final mounting bolt torque retention and good concentricity after having windings placed thereon and then being bolted to compressor mounting means.
Accordingly, an object of the present invention is to provide new and improved apparatus that can be utilized to produce unbonded stator cores and/or stator assemblies that will exhibit good bore concentricity and good bolt torque (or tension) retention characteristics.